The present invention relates to a high resolution scanner, and in particular to a high resolution scanner using a disc, such as a laser disc or compact disc, to provide accurate traceability.
A typical scanner is a flatbed scanner based on charge coupled device (CCD) technology. An operator puts an original on the flatbed scanner to read or scan the image. The scanner illuminates the original with a scanning light from a light source and the CCD optically detects the passed or reflected light through or from the original. The resolution of the flatbed scanner depends on the density of the CCD and is limited by the mechanical accuracy of the scanning of the light source and optical detector. However high density CCDs may cause interference with light from adjacent pixels when each pixel of the CCD reads each pixel of the image of the original, thus degrading the image data. To eliminate this problem many and complicated scans of the image are required.
Another type of scanner is a drum scanner which may provide a high resolution image by reading each pixel of an image independently in space or in time. The drum scanner has a rotatable transparent drum and the original, such as a photographic film, is attached to the surface of the drum. The scanner also has a light source slidably placed on the rotation axis of the drum and an optical detector positioned parallel to the surface of the drum for reading the original. The light source and optical detector face each other via the cylindrical dram surface and move together along the axis of the dram to scan the original. The detector thus reads or scans the original while the dram rotates. The accuracy of the scanning mainly depends on the mechanical configuration between the light source and the detector relative to the drum. The position control mechanism keeps the drum structure in parallel to the rotation axis via a screw, and turns the screw using a motor to slide the light source and detector along the axis. The precise scan requires that the movement of the optical detector is a linear function of the rotation of the motor. As a result the screw needs to be milled precisely, with errors on the order of micrometers. The manufacturing of such a precise screw needs large machine tools which leads to high cost. A further disadvantage of the drum scanner is that the original source of the image being scanned needs to be flexible to fit around the surface of the drum.
What is desired is an inexpensive disc high resolution scanner that reads pixels independently in space or in time without requiring that the original source be flexible.